My boiler keeps turning the central heating on by itself?

[tommy1306]

hi there. can any one help?

i have a potterton combi 80 boiler. at the moment it is set to only supply hot water with no central heating. but for some reason it keeps turning on the central heating every now and then. it simply has 2 rocker switches.
1. to turn the boiler on or set it to standby
2. to turn the central heating to timed,constant,and off.
and a timer switch with 15min segments to set the times you want it to turn on/off.
it has no central thermostat control. the radiators have thermostats fitted.

switch 1 is set to on at the moment.
switch 2 is set to off.
and the timer wheel has no segments pushed in.

does any one have any ideas as to why the central heating turns itself on when it set set to be off?
the radiators get very hot quickly.

thanks for your time.

 

[kevplumb]

have a look round the area of the hot water flow switch

 

[picasso]

If it aint the flow switch sticking it might be the internal frost stat kicking in, normally its the primary thermistor that acts as the f/stat so might need checking .